Machine-to-Machine Authentication (M2M Tokens)

What is Machine-to-Machine (M2M) Authentication?

Machine-to-machine (M2M) authentication is the process of allowing two applications or services to communicate securely without a user present. Instead of passwords or API keys, each service uses its own Client ID and Client Secret to request a short-lived access token. This ensures secure, auditable, and revocable service-to-service authentication, widely used in backend integrations, microservices, and IoT systems.

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Benefits of using M2M tokens

Improved Security

Uses short-lived, revocable tokens instead of long-term static credentials.

Fully Automated

Enables systems to authenticate without human input.

Fine-Grained Access Control

Limit machine access to only the necessary resources.

Highly Scalable

Handles a large fleet of devices or services and requests with ease.

Regulatory Compliance and Auditability

Tracks when and how machines access resources.

Industry Standard Protocols

Compatible with established frameworks like OAuth 2.0 and JWT.

Common Use Cases

Application Backends

Securely transfer data, logs, or files between internal and external services.

CLI Tools

Let command-line tools securely access APIs using short-lived, scoped tokens.

Scheduled Jobs & Daemons

Authorize cronjobs, job schedulers, and background workers to interact with APIs safely and efficiently.

IoT Devices

Enable smart devices to send data to your cloud services automatically for telemetry or commands, with each device authenticated and scoped individually.

How it Works

Register Your Resources

Add APIs to Authgear and define the scopes (permissions) for each of them

Register Your Application

Create a client application for each backend, device, or tool that needs API access. Assign the resources and scopes available to the service

Obtain Credentials

Each application receives a unique client ID and secret

Request a Token

The application authenticates with Authgear using the /oauth/token endpoint, and receives a short-lived access token, containing only the scopes you've assigned.

Access Protected APIs

The service uses the bearer token in the Authorization header to call your APIs

Frequently Asked Questions (FAQ)

What is machine-to-machine (M2M) authentication?

M2M authentication is a method that allows services or applications to securely communicate without user credentials. Instead, services exchange M2M tokens (short-lived access tokens) via the OAuth Client Credentials Flow.

How does the OAuth Client Credentials Flow work?

The Client Credentials Flow issues an access token directly to a machine or service (not a user). A service authenticates using its Client ID and Secret and receives a JWT token it can use to access protected APIs.

Why use M2M tokens instead of API keys?

M2M tokens are short-lived, scoped, and revocable. Unlike static API keys, they improve security by limiting exposure and allowing fine-grained access control.

Can I use M2M authentication for microservices?

Yes. M2M authentication is commonly used for microservice-to-microservice communication, ensuring secure backend API calls without embedding static secrets.

Secure Machine-to-Machine (M2M) Authentication with Authgear